1. Field of the Invention
The invention concerns a comparator circuit for an integrator.
2. Prior Art
In many electrical circuits it is necessary to detect the level of signals and to alter the logic level of output signals depending on the momentary value of this level, for example, for ramp function generators using an integrator.
The comparator function can be implemented by using integrated comparators, for example, the LM 111 model from the manufacturer National Semiconductor. The integrator function can be implemented, for example, by using an operational amplifier of type 741 or a regenerative (feedback) transistor. A combination of both can be integrated on one chip.
However, for a defined operating manner of the comparator, its input voltage must normally lie in a range of approximately 1 to 2 volts above the ground potential and about 1 to 2 volts below the operating voltage. The range of input voltage which can be exploited is therefore clearly limited with respect to the operating voltage.
There are comparators, for example type LM 193 from the manufacturer National Semiconductor, with which the input voltage can be utilized up to the ground potential. However, the upper limit of the input voltage range for this type also lies approximately 1 to 2 volts below the operating voltage.
Apart from that, the circuits for such comparators are relatively expensive and an integrated comparator circuit for an integrator would require a relatively large chip area.